Please give us some more detail on the sail sizes for medium/high wind, that will influence the best choice (or recommendations etc)

Yes, you can use V8 9.8m with C144 but it will be right at the upper limit of sail /power size, not so good or responsive handling but better than sitting on the beach. A larger fin will help in marginal (9.8m) conditions, consider around 52-54cm.(but not more, considering the narrower tail c/w FT etc for this volume)